Method of fastening tubes in headers or tube plates



F. M. YOUNG y 2,368,391

Jan. 30, 1945.

METHOD OF FASTENING TUBES IN READERS OR TUBE APLATES' I Filed May 23, 1942 ,IF Il N KNEW , INVENTOR. ein /7 )6a/v@ ATTOIZNEY Patented Jan. 30, 1945 METHOD FASTENING TUBES IN HEAD- ERS R TUBE PLATES Fred M. Young, Racine, Wis. Application May 23. 1942, sei-n1 No. 444,198

2 claims. (ci. 285-111) The sensitive nature of copper as to overheat.

ing has'- made it dilcult to lsecure thin walled copper tubes to heat exchanger headers and tube plates. One cause of this difficulty` is the factl that the tube plates or walls of the headers are very much thicker than the thickness of the walls of the tubes andthe fact that some modern heat exchangers have steel tube plates or headers which require a bonding either by brazing or electric welding either of which require high temperature. The difficulty of brazing a very thin walled tube to a relatively thick tube plate or header wall is increased because-the tube wall is very thin and may be burned before the heavier member reaches the fusion bonding temperature.

Copper is considered a precious metal and therefore the walls of the tubes must be very thin.. `In many cases lthese walls Yare not over .025 inch thick whereas the tube plate may be one eighth inch thick or even more.

One of the difficulties in copper tube heat exchangers is that the tubes are easily fractured. This difficulty is multiplied many times by the fact that there is usually considerable vibration either set up by the action of the fan motor, the

ment, one injured tube in the lotl will seriously effect the value of theexchanger when completedl because whenfa. single tube of the lot is fractured, the entire exchanger may be ruined.

. An object of the present invention is to provide a design in which overheating of a single tube in an assembly is eliminated even i1 the opera- Vtion is in the hands of a workman inclined lto be a bit careless at times.

In my design, means are provided whereby if the completed exchanger passes the leak-proof test there will be no danger of subsequent fracture because the tubes are protected against vibration at the point where they are secured to the header.

I accomplish the objects of this invention by supplying relatively thick walled sleeves of a suitable length which are brazed to the ends of the tubes, after which the sleeves are inserted into cular pipe header taken through a the openings in the header or tube plate then I the 'outside surfaces of the sleeves are preferably electric welded to the header or tube plate.'

The invention isapplicable to structures where lthe headers or tube plates and sleeves are steel and the weld between the header or tube plate is a considerable distance from the brazing at the tube ends; thus making it possible to braze the tube tothe end of steel sleeves and electric weld the sleeves to the tube plate or header without danger of injuring'the tubes or the 'brazing` To these and other useful ends, my invention i consists of parts, combinations of parts, or their equivalents, and mode of. operation, as hereinafter set forth andclaimed and shown in the accompanying drawing in which:

Fig. 1 is a transverse sectional view oi a cirsleeve and a fraction o f the tube.

Fig. 2 is 'a sectional view through a fraction 0f a tube plate wherein the tube is secured to va ilat tube plate.

Fig. 3 illustrates a fraction of a core and a tube plate of a heat exchanger ready to be assembled.

As thus illustrated in Figure l, numeral III designates a header which is generally made from steel and having considerable thickness as illustrated, so it is suitable for high pressure steam. Numeral I I designates a steel sleeve having preferably a wall thickness about'equal to the thickness of the header tube wall and having a length preferably about as illustrated. Sleeve I I is counter-bored at its inner end as at I2 and flared at the other end as at I3. The tube is designated by lreference numeral I4 which, as will be noted, has a. comparatively thin wall and is generally made from copper or a copper alloy.

Tubes I4 preferably protrude a short distance through the ends of sleeves II as illustrated; thus an annular trench is provided by counterbore I2 forming a suitable receptacle for the brazing material I5 without danger of getting the spelter in the tube or on the outside of the sleeve and providing means whereby the brazing can be done without danger of overheating the tube.

In building a heat, exchanger of the class, the core comprises a numbercf tubes I4 having a multiplicity of spaced ns I I' through .which the tubes extend. Afterthe tubes and fins are assembled into a core, as fractionally illustrated in Figure /3, sleeves II are positioned on the ends of the tubes as illustrated and brazed thereto as at I5. Openings I8 are provided in tube plate I9 or circular header I0 adapted to register with the tubes and sleeves of the core and after the operation oi' securing the sleeves tc the ends of the tubes. as illustrated in Figure 3, the tube ends and sleeves are inserted into the openings as illustrated in Figures 1 or 2. after which the sleeves are electric welded or brazed to the tube plates or tube header as at 2li.

It will be seen that I have provided a strong and emcient heat exchanger which will be practicaily proof against defects and may be manufactured in a manner which insures against deiecte even when the assembler is not highly trained By referring to Figures 1 and 2, it will be seen that braaings IB and welds 2l are a considerable distance apart and that they are remote from the point where the tube enters the sleeve, that this latter point provides a gradually increased opening .through which the tube extends so as to avoid the possibility of fractures from vibration oi the portion of the rtube which has been slightly weakened during the rst brazing operation.

It will also be seen that the high temperature required for electric welding the sleeves to the tube plates or headers cannot possibly injure the brand joint or the tube even if the electric weld is necessary on the tube end side of plate I9.

Clearly one of the reasons why my design and method are successful is the fact that steel is comparatively not a good heat conductor so when weld Il is made, there is no danger o! iniuring the braced Joint il or the tube and when brazing as atll, close contact with sleeve Il will prevent overheating tube Il.

l a tube having mounted 0n its end a relatively long and thick walled sleeve, their ends being adjacent and brazed or hard soldered together, a relatively thick tube plate having an opening adapted to snugly receive said sleeve after said bonding operation, said sleeve and plate being then welded or brazed together on the opposite side of said. tube plate from said brazed ends, the sleeve on the end adjacent said tube end being countersunk for the reception of the brazing material and the opening in the other end of said sleeve being ilared.

2. A device of the class described, comprising a number of spaced tubes and a multiplicity of closely spaced fins through which the tubes extend forming a core, sleeves having relatively thick walls and being relatively long and positioned on said tubes, the tube and sleeve ends being adjacent and bonded together. a header inclosure having apertures adapted for the Snug reception of said sleeves en masse. said sleeves and header being then secured together by brazing or welding at a point remote from said first bond, the tube end of said sleeve being counterbored i'or the reception of the Ibrazingf material, the opening in the other end of the sleeve being dared.

FRED M. YQUNG. 

